1. Field of the Invention
The present general inventive concept relates to an image forming apparatus and a sensing device thereof, and more particularly, to an image forming apparatus and a sensing device thereof capable of removing pollutants attached to a sensor.
2. Description of the Related Art
Generally, an image forming apparatus is an apparatus to print an image on paper according to input signals. Examples of the image forming apparatus include printers, copiers, facsimiles, devices combining functions thereof, and the like.
In the image forming apparatus, a light beam is irradiated onto a photosensitive member charged with a predetermined electric potential, to form an electrostatic latent image on a surface of the photosensitive member. Then, a developer is fed to the electrostatic latent image, forming a visible developer image. The developer image, formed on the photosensitive member, is transferred to a printing medium directly or by way of an intermediate transfer medium, and the transferred image is fixed to the printing medium via a fixing process. To prevent a next printing medium from being stained with a developer residue during sequential printing operations, an operation to remove the developer residue remaining on the photosensitive member is performed.
In an operation of forming the developer image by feeding the developer to the photosensitive member formed with the electrostatic latent image, if the developer is not uniformly fed to the photosensitive member, the developer cannot be fed to a desired region where the electrostatic latent image is formed, or the developer can be attached to a region except for the electrostatic latent image region, resulting in deterioration in print quality. Therefore, maintaining a desired constant thickness of a developer layer to be attached to the photosensitive member is important to maintain a constant print quality and to prevent waste of the developer. Attachment degree of the developer in relation to the photosensitive member is determined on the basis of physical and chemical properties of the developer, mounting position of a regulating blade provided in a developing container, etc.
A sensor is provided near the photosensitive member, to sense whether or not an appropriate density of developer is attached to the photosensitive member or whether or not a background phenomenon representing an irregular developer layer occurs.
However, with the conventional image forming apparatus and a sensing device thereof, since the sensor is attached to the photosensitive member or located only near the photosensitive member to sense whether or not the density of the developer, the sensor is exposed to the scattered developer. In addition, if the sensor is located in proximity to a printing medium delivery path, paper dust released from a printing medium may accumulate on the sensor. When the sensor is polluted (contaminated) with the developer, etc., it prevent a normal operation of the sensor and therefore, pollutants (contaminants) to be removed.
To remove pollutants (contaminants) accumulated on the sensor, there has been proposed a method to manually wash the sensor periodically so as to maintain functions of the sensor, or to provide the sensor with a complex configuration of a cleaning device. However, these proposed methods disadvantageously increase user's inconvenience or the price of the image forming apparatus.